Multi-axis Motion Research Articles

Trajectory modification method based on frequency domain analysis for precision contouring motion control systems

For multi-axis motion system widely used in CNC machine tools, contouring following control is an important research topic. For most existing contouring motion control methods, it is usually necessary to estimate the contouring error of multi-axis system and then design contouring controller to suppress it. However, additional contouring error estimator and controller requiring complicated hardware adjustment is not suitable for existing commercial CNC systems with built-in control systems. In this paper, a frequency domain analysis based trajectory modification method is proposed to improve contouring control performance through a way that is easier to implement. In the proposed method, the modified trajectory can be calculated off-line just according to the instantaneous frequencies of the reference trajectories and the closed loop frequency characteristics of each axis. After the modification, the amplitude attenuation of the actual position output can be effectively suppressed, and the output of each axis has the same phase lag, thus improving the contouring control performance. Compared with other existing contouring control methods, the main contribution of this paper is to analyze and control contouring error from the angle of frequency. Various of simulations and comparative experiments are conducted to verify the effectiveness of the proposed contouring control method. The experimental results demonstrate the advantages of the proposed scheme over other methods, i.e. excellent contouring control performance can be achieved without additional contouring error estimation and control.

Design of a Multi-axis Motion Control Platform Based on LabVIEW’s Fuzzy Control Algorithm

Design of a Multi-axis Motion Control Platform Based on LabVIEW’s Fuzzy Control Algorithm

A Novel Intermediate Estimator Based Secure Consensus Control for Multi-agent Systems with Application to Networked Multi-axis Motion Synchronization

This paper studies the secure consensus control problem of multi-agent systems under DoS attacks on the sensor, the actuator, and the communication topology. A resilient intermediate estimator based attack tolerant control strategy is proposed. By fully exploiting the hardware redundancies, both of the estimators and the control protocols can be reconstructed online according to different DoS attack scenarios. Finally, the experiment results of the networked multi-axis motion control system are given to verify the effectiveness of the proposed method.

Topology reconstruction based fault identification for uncertain multi-agent systems with application to multi-axis motion control system

In the industrial multi-agent systems, the effect of the faults occurring on any subsystem may diffuse to the whole system through network topology and cause the control performance degradation. This paper aims to solve the issue of fault identification for uncertain multi-agent systems with sensor faults. Firstly, a randomized cooperative fault detection system composed by a group of decoupled filters is presented, where a joint fault detection performance assessment scheme is designed. On this basis, a novel topology reconstruction-based fault isolation strategy is proposed. Finally, two case studies on the multi-axis motion control system are conducted, and the results illustrate the effectiveness of the proposed framework.

The Visible Korean: movable surface models of the hip joint.

In this study, we presented movable surface models to help medical students understand the multiaxial movements of the hip joint. The secondary objective was to demonstrate a simple method to make movable surface models for other researchers. We used 166 surface models of the virtual human, and the commercial software was used for all the processes described in this study. Virtual joints were created for the hip joint of the surface models to simulate realistic movements of the joints. Bone surface models were processed to maintain the original shape of the bones during movement. Muscle surface models were processed to express deformation of the muscle shapes during movement. Next, the muscle and bone surface models were moved over six movements of the hip joint (flexion, extension, abduction, adduction, lateral rotation, and medial rotation). The surface models of these six movements were saved and packaged in a PDF file. The PDF file enabled users to see the stereoscopic shapes of the bones and muscles of the hip joint and to scrutinize the six movements on the X, Y, and Z axes of the joint. The movable surface models of the hip joint of this study will be helpful for medical students to learn the multiaxial movements of the hip joint. We expect to develop simulations of other joints that can be used in the education of medical students using the materials and methods described in this study.

Spherical center axial hinge knee prosthesis causes lower contact stress on tibial insert and bushing compared with biaxial hinge knee prosthesis

BackgroundMotion axial system may affect contact stress of hinge knee prosthesis. However, it is unclear which axial system provides the better biomechanical effect. Therefore, the aim of this study was to compare the contact stress and stress distribution on the tibial insert and the bushing of hinge knee prostheses with a biaxial (BA) system and a spherical center axial (SA) system during a gait cycle. MethodsThree-dimensional finite-element (FE) models of the prostheses with different motion systems were included. The comparisons between experimental tests and FE analyses were performed to verify the models. Dynamic implicit FE analyses were performed to investigate the peak contact stresses and stress distributions on the tibial insert and the bushing. ResultsThe peak contact stresses on the tibial insert and the bushing of the BA prosthesis were higher than those of the SA prosthesis during most gait cycles. The contact time on the bushing is short in the SA prosthesis. The stress distributions on the superior surface of the tibial insert in the BA prosthesis were at the posterior side, but of the SA prosthesis were not fixed. ConclusionThe SA prosthesis has a lower peak contact stress on tibial insert and bushing than the BA prosthesis; in addition, the SA prosthesis has a ‘self-adjustment’ mechanism which could disperse high stress on the tibial insert to decrease the risk of wear and damage. The comparison could help designers and surgeons to better understand the future design of rotating hinge knee prostheses which should be able to achieve multiaxial motion and complete weight bearing by the tibial condylar to transmit the axial force better.

Curved Layer Slicing based on Isothermal Surface

Conventional slicing algorithms for additive manufacturing (AM) processes slice the designed model into a set of planar layers, due to the simplicity, robustness, and generality of most geometries. However, such planar-layer-based slicing significantly limits the performance of the AM system with stair-stepping surface finishing, massive supporting structures, non-conformable to curved substrates, and reduced strength for thin shell structures. To mitigate these drawbacks of planar layer slicing, we presented a curved layer slicing method by utilizing the isothermal surfaces in heat transfer simulation. The designed part is virtually placed on a heated substrate, and the heat spread out through the part, which establishes a temperature field. The isothermal surfaces of this temperature field naturally create curved layers for the printing process. Our method successfully generated curved layers and tool paths for additive manufacturing processes with three-axis and multi-axis 3D printing. A multi-axis motion 3D printing machine is developed based on fused decomposition modeling (FDM). Several test cases were performed to verify and demonstrate our slicing method’s capabilities. A discussion of future development on our general non-planar slicing system was also given.

High-precision video acquisition system based on three-axis linkage

The main research content of this system is to realize the linkage control of multi-axis motor through LabVIEW and single chip microcomputer. The operator can operate the upper computer software to send the speed and spatial coordinate instructions remotely. The expansion chip ch438q is used to store temporarily, and then the data is transmitted to the processor of max13487 for control. According to the RS485 serial port communication mode, the analyzed data parameter information is transmitted In the stc15 single-chip microcomputer on four single axis control cards, the motor is controlled by the driver to make the controlled object move to the specified position quickly and accurately. In the process of movement, the upper computer can display x, y in real time. In order to test and use the system to achieve certain functions, a set of high-precision multi angle video acquisition system based on three-axis linkage and four axis control is designed. The selected camera is a 120°wide-angle camera, which can make the range of scenery observed from a certain point of view much larger than that of human eyes in the same view point Monitoring. After many experiments, the accuracy of the system can reach 1μM. The system itself can also expand a variety of functions according to different needs, which has a certain practical value.

Early and medium-term results of total joint arthroplasty of first carpo-metacarpal joint

Introduction. Reviews dedicated to surgical treatment of the first carpo-metacarpal joint repeatedly state that the evaluation of arthroplasty results is difficult. This is due to the small clinical study groups and the lack of description of all types of outcomes.
 The aim of the study is to analyze obtained early and midterm results of ceramic CMC-arthroplasty. The endoprosthesis are represented with unbound proximal and distal components made of ceramic material. The interaction of the head and cup is represented with no intersecting forces that impede on the multi-axial movement. The surgical technique of CMC-1 joint arthroplasty prescribes the installation of components by the press-fit fixation. There is a brief emphasis on the features of the joint and contributing factors for the development of risarthrosis. Early results are described. Cases of unsatisfactory outcomes are described separately.
 Materials and methods. The study group included patients from 33 to 72 years. The total number of observers was 28 people. We performed revision endoprosthetics in 2 cases (7%), which were associated with aseptic instability of the proximal component according to the osteoporosis. It obvious that endoprosthetics is the only method of orthopedic care that allows maintain mobility and achieve stability of the destroyed CMC joint. Evaluation of the results was carried out by clinical and instrumental methods.
 Results. It cannot be denied that the CMC arthroplasty is the only method of orthopedic care that allows to preserve mobility and achieve stability of the broken joint.
 Conclusion. Arthroplasty of the carpo-metacarpal joint with ceramic implants is a promising method of orthopedic care, that allows to restore the function of the hand.

Prediction-Model-Based Contouring Error Iterative Precompensation Scheme for Precision Multiaxis Motion Systems

In order to achieve both accurate contouring error estimation and excellent contouring control performance for multiaxis motion systems, this article proposes an online iterative precompensation control method based on a third-order contouring error prediction model. Specifically, the closed-loop dynamical model of each axis is first used to predict tracking errors at future sampling instants. And then the related contouring error of the multiaxis system at future time can be expressed by the predicted tracking error and the theoretical third-order model of the reference contour. To reduce the influence of modeling error and uncertain disturbances on the prediction performance of contouring error, the numerical calculation method is utilized to obtain absolutely accurate contouring error, through which the deviation between the proposed contouring error model and the accurate one can be corrected accordingly. Based on the accurate contouring error prediction model, the optimal contouring error compensation can be generated through online iterative calculation. To achieve excellent contouring performance, the compensation is added to the original reference contour as a kind of trajectory precompensation. Comparative experiments are carried out on an industrial three-axis machine tool. A series of contour tracking experiments consistently demonstrate that the proposed method can predicate the contouring error accurately. Additionally, the contouring motion performance can also be significantly improved in the case of a variety of different trajectories.

The Restoration of the Function of the Thumb using Sequential Arthroplasty of the Trapeziometacarpal and Metacarpophalangeal Joints

Background. The opposition function of the thumb is extremely important and is provided mainly due to the biomechanical features of the trapeziometacarpal and metacarpophalangeal joints. Surgical treatment of complex deformities of these joints is often described in isolated studies, and there are practically no descriptions of the results of their combined treatment. The authors of the article did not find a single report on total arthroplasty of the adjacent joints of the thumb. Aim of the study. To analyze the clinical observation of two patients in the early period after performing sequential non-simultaneous total arthroplasty of the trapeziometacarpal and metacarpophalangeal joints of the thumb using ceramic endoprostheses. Both endoprostheses were presented in pairs with two unconnected components, installed using the press-fit method. When the head and cup interact, there are no shear forces in them that impede multiaxial movements. Materials and methods . The study included two patients: a 67-year-old man and a 77-year-old woman. Patients had stage 3 osteoarthritis of the trapeziometacarpal and metacarpophalangeal joints of the thumb and underwent staged surgical treatment (about 2–3 years between the stages). In 1 month and 1 year after the treatment we assessed the results using clinical and instrumental research methods. Conclusion. No complications were observed during the follow-up. There were no indications for revision surgery. The design features of ceramic endoprostheses, due to their short stems, make it possible to combine components in the adjacent joints of the thumb. In our opinion, joint arthroplasty is an effective and promising method of functional restoration. It remains the patient’s last hope for maintaining painless, stable mobility of the thumb.

Design and Implementation of a Network Based Multi-Axis Motion Control System for Laboratory Studies

In this study, an open source network based three axis motion control system has been designed and implemented to be used within motion control courses at engineering and technical branches for applicational studies. This system has been developed by using open source code and suitable physical structure for engineering studies. This experimental set has been evaluated by 107 students in related courses which are electrical machines and servo systems. Students have conducted various experiments by using single, two and three axes respectively. These students have been subjected to a Learner Satisfaction Survey which focuses on cognitive, affective and psychomotor extend of experimental studies in the laboratory with the designed motion control system. It has been observed from the results of this survey that learner-centered approach with the experimental set contribute in learning process positively.

On multi-axis motion synchronization: The cascade control structure and integrated SMC–ADRC design

In this paper, the cascade control (CC), a structure popular among practitioners in many industry sectors, is used to bridge the two prominent research methodologies in SMC and ADRC for the purpose of multi-axis motion synchronization. In particular, the cascade sliding mode control(C-SMC) is first proposed, from which the cascade active disturbance rejection control (C-ADRC) is derived. This allows the linear and fal-function based nonlinear control actions to be naturally integrated and the controller parameters can be tuned easily with the proposed space–time scaling method. The control law is constructed and validated in multi-axis motion synchronization of parallel mechanisms. The results show that the proposed scheme is effective and practical, with the robustness associated with the bandwidth constraints.

Optimized geometric error sensitivity analysis approach based on stream-of-variation theory in multi-axis precise motion platform

In this paper, an optimized error sensitivity analysis (ESA) approach based on stream-of-variation (SOV) theory in multi-axis precise motion platform (MPMP) is introduced. Unlike the conventional ESA method, this approach utilizes stream-of-variation theory to establish error model firstly. By regarding each axis as a station, the error propagation and deviation accumulation processes are clear station by station. Through obtaining the deviations after each station, the sensitive stations can be developed, and corresponding error terms are collected. Thus, by analyzing the appearance frequency of the errors, a precise sensitive order can be developed, and a sensitivity results with different steps is given. Through ignoring the insensitive and irrelevant errors, the computational volume of error model can be saved, and the efficiency can be improved. A case study about a typical MPMP used in laser welding system (LWS) is carried out, and the results indicate that the optimized ESA approach is more efficient and accurate, and it is flexible as well. This ESA approach is not only accurate in developing sensitive levels, but also balancing the systematic accuracy and working efficiency, which is helpful to provide informative guide to engineers.

Farklı Mıknatıs Yapıları ve Farklı Mıknatıs Malzemeleri Kullanımının Küresel Motorun Tasarımına Etkisi

Today, with the advances in technology, the need for motors capable of multi-degree of freedom in robotic systems, medicine, automotive industry and industrial applications is increasing. For this reason, in this study, a permanent magnet spherical motor design with multi-axis motion ability has been designed and electromagnetic analysis has been done with ANSYS Maxwell software using the finite element method. In the analysis, motor designs were made by considering different types of magnets in the rotor and different lamination types in the stator and rotor cores with different magnet structures. Electromagnetic analyzes were performed for each model created using steel_1008, M43_24G, JFE_Steel_50JNE300 materials in stator and rotor structures and NdFe30, NdFe35, SmCo28 materials as magnets with embedded straigt magnet, embedded V-type magnet, surface magnet structures.For each design, magnetic saturation problem of magnetic flux density distribution is examined, moment and force values are calculated and results are given comparatively.

Design, modelling and validation of a novel extra slender continuum robot for in-situ inspection and repair in aeroengine

In-situ aeroengine maintenance works are highly beneficial as it can significantly reduce the current maintenance cycle which is extensive and costly due to the disassembly requirement of engines from aircraft. However, navigating in/out via inspection ports and performing multi-axis movements with end-effectors in constrained environments (e.g. combustion chamber) is fairly challenging. A novel extra-slender (diameter-to-length ratio < 0.02) dual-stage continuum robot (16 degree-of-freedom) is proposed to navigate in and out confined environments and perform required configuration shapes for repair operations. Firstly, the robot design presents several innovative mechatronic solutions: (i) dual-stage tendon-driven structure with bevelled disks to perform required shapes and to provide selective stiffness for carrying high payloads; (ii) various rigid-compliant combined joints to enable different flexibility and stiffness in each stage; (iii) three commanding cables for each 2-DoF section to minimise the number of actuators with precise actuation. Secondly, a segment-scaled piecewise-constant-curvature-theory based kinematic model and a Kirchhoff-elastic-rod-theory based static model are established by considering the applied forces/moments (friction, actuation, gravity and external load), where the friction coefficient is modelled as a function of bending angle. Finally, experiments were carried out to validate the proposed static modelling and to evaluate the robot capabilities of performing the predefined shape and stiffness.

Hybrid directed energy deposition for fabricating metal structures with embedded sensors

Hybrid additive manufacturing combines additive manufacturing (AM) and traditional subtractive processing with synergistic layerwise access. The integration of both manufacturing methods simultaneously enables the benefits of AM (complex geometries and mass customization) with the benefits of traditional processes (superior surface finish and improved dimensional accuracies). By leveraging access to the structure at intermediate layers during fabrication with a suite of additional processes (e.g. component placement and micro-dispensing of functional inks, machining, etc.), the next generation of metal structural elements with printed internal sensors can be fabricated without the need for specific tooling (i.e. optical masks). A multi-axis motion platform allows the printing of sensors in arbitrary planes and on curved surfaces that can be subsequently embedded within the structure using additional laser cladding. Embedded printed sensors in metal have been demonstrated for decades in additive manufacturing, but have required tooling and disparate processing steps unsuitable for integration within AM directly. In this report, an Ambit™ system was used to fabricate a proof-of-concept tensile bar with an embedded thick-film printed strain sensor, and consequently, the potential for digital fabrication of multi-functional metal structures within a single manufacturing system without tooling was demonstrated. Careful process planning and thermal shielding are required to ensure the survival of printed sensors during the final high-temperature consolidation. A study was conducted to investigate the required thickness of protective plates, and for the thickness of 2.25 mm, sensors were functional. Both in situ and post-manufacturing data were captured. Failure analysis was performed on the non-operational sensors to understand the challenges of the proposed approach.

A New Observer-Based Cooperative Fault-Tolerant Tracking Control Method With Application to Networked Multiaxis Motion Control System

In a networked multiaxis motion control task, faults in any motor will cause the performance degradation of cooperative operation, which may considerably affect the whole network and the quality of products. The main objective of this article is to propose an improved observer-based fault-tolerant tracking control approach for industrial multiagent systems. First, a group of new distributed intermediate estimators is presented, where the design structure is modified to enhance the feasibility of the estimation scheme. It is shown that both of the nominal distributed intermediate estimator and the traditional extended state observer are special cases of the proposed estimator. Second, the estimation performance can be improved significantly via an online reinforcement learning estimation strategy, whose core is an adaptive switching mechanism integrated with a function block of source fault mode localization. Benefiting from satisfactory estimation results, good fault-tolerant tracking control performance can be guaranteed despite of multiple faults and disturbances. The application to a networked multiaxis motion control system demonstrates the effectiveness and superiority of the proposed method.

Cooperative attack tolerant tracking control for multi-agent system with a resilient switching scheme

This paper studies the cooperative attack tolerant tracking control problem for multi-agent systems under sensor attacks. A group of distributed adaptive state observers with a resilient switching scheme is proposed to reconstruct the states, then the tracking control strategy is designed based on the estimates. It is shown that both of the estimation and the attack tolerance control performances are ensured despite of multiple sensor attacks and the disturbances. Finally, the experimental results of networked multi-axis motion control show the effectiveness of the proposed method.

Advances in grinding technology in China with application in steel roller manufacturing

Grinding of large or ultralarge components to achieve stringent quality is always challenging in China’s manufacturing industry, for example, roller for steel strip production. Compared with transverse cylindrical grinding, roller grinding requires high-precision multiaxis motion. In addition, with the increasing demand for process efficiency, the in-process measurement and process compensation become necessary for higher process reliability and productivity. This article presents the state-of-the-art and emerging technology in China’s roller grinding, which includes heavy-duty grinding machine optimization, high-performance tooling design, in-process geometrical accuracy compensation, in-site machine vision for gloss defect, and intelligent process parameter optimization strategy. Therefore, this article will shed light on the development trend of the enabling technology toward intelligent roller grinding with higher accuracy, dexterity, and efficiency.