Multi-axis Motion Control System Research Articles

Design and test of an efficient seedling pick-up device with a combination of air jet ejection and mechanical action

Low degree of transplanting automation will affect production efficiency and planting quality in vegetable cultivation. A new seedling pick-up device was designed and constructed to reduce direct grasping damages to seedlings and improve transplanting efficiency. The pick-up device consists of an air jet loosening device, a flexible pick-up manipulator, a parallel feeding device, and a multi-axis motion control system. Its working principle is to use air jet ejection to assist in loosening of seedling roots from the tray cells, grasp their stems for extracting with the pick-up manipulator, and finally transfer them to the delivery device for feeding into the planting device as needed. The mechanical structure and working parameters of each component were designed, and the control system was constructed according to the working requirements of ejecting, extracting, transferring, and discharging operations. A prototype of the new pick-up device was constructed, and its performance evaluation was conducted using an orthogonal experimental design using cucumber, pepper and caluiflower as test objects. The results showed that the test object, the root lump's moisture content and the loosening way (either as a whole or individual loosening of seedlings) had significant effects on the success ratio in picking up seedlings. Overall, the success in picking up seedlings from the cell was found to be influenced by horticultural and mechanical factors. Under the optimal level group, the maximum success ratio for automatic picking up seedlings was up to 94.49% for pepper while that of cucumber and cauliflower recorded 90.75% and 92.62%, respectively. The seedling pick-up performance was satisfactory for efficient transplanting requirements.

Contour error dynamic analysis and predictive control for multi-axis motion system

Contour tracking accuracy is the key performance index of a multi-axis motion control system. In the previous design of the contour error feedback controller, the independent design idea of the tracking controller and contour controller of each logic axis is often adopted, which is not easy to realize the optimal control of tracking accuracy and contour accuracy. The coupling increment of each controller is inevitable in motion control compensation, which impacts the control system’s stability. Here, we propose a predictive control method for contour error. At first, through the state space model of the feed system, the system dynamics are judged to predict the contour accuracy in the future finite time domain. Besides, the linear quadratic performance index function of contour error is established, and the performance of the control objective is continuously optimized during the limited time domain with the form of rolling optimization. A closed-loop solution is obtained, which is most suitable for the current motion situation and could add to the system to realize the optimal control considering the trajectory contour and the tracking stability of each servo axis in the subsequent few sampling cycles. Finally, utilizing comparative experiments on the three-axis motion control platform, it is verified that the proposed contour predictive control strategy not only effectively reduces the tracking error but also significantly improves the contour accuracy, which is suitable for application in a complex industrial environment.

Circular Subaperture Stitching Interferometry Based on Polarization Grating and Virtual–Real Combination Interferometer

This paper presents a polarization grating based circular subaperture stitching interferometer. The system can be used for small F/# concave surface tests with a large F/# transmission sphere, where F/# is the ratio of focal length to aperture. A polarization grating was employed to deflect the incident beam for subaperture scanning by its axial rotation instead of a multi-axis motion-control system. Compared with the traditional subaperture stitching interferometric system, the system proposed in this paper is smaller in size and reduces the measurement error introduced by mechanical adjustment. Using a virtual interferometer model and a virtual-real combination algorithm to remove the retrace error, the full-aperture figure error can be directly obtained without the need for a complex stitching algorithm. The feasibility of the algorithm was verified, and the measurement error caused by the modeling error was analyzed by simulation. The capability of the polarization grating to scan subapertures was experimentally confirmed, and possible solutions to some engineering challenges were pointed out. The research in this paper has pioneering and guiding significance for the application of polarization grating in interferometry.

A Study on Intelligent GIS Installation System Based on Six-DOF Parallel Multi-axis Motion Control

Aiming at the connection of pipelines during the GIS installation process of power transmission and transformation projects, this subject designs and produces an intelligent GIS installation system based on 6-DOF parallel multi-axis motion control, which is applied to practical applications. The intelligent installation system can realize six independent motions and their combined motions in three-dimensional space. Relying on the multi-dimensional visual positioning system, through the six-degree-of-freedom parallel multi-axis motion control system, the precise docking during the installation of the precision GIS cavity can be realized.

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.

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.

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.

Contour Tracking Control of Networked Motion Control System Using Improved Equivalent-Input-Disturbance Approach

This article deals with contour tracking control of a networked multiaxis motion control system with repetitive tasks. To improve the control performance of the system under the overall effects of aperiodic time-varying delays and exogenous disturbances, a network-induced delay is first modeled to be a disturbance. Next, an improved equivalent-input-disturbance (IEID) approach is devised to suppress the overall effect. Then, an iterative learning controller is designed in combination with the IEID estimator to perform individual-axis tracking control. The stability of the system is analyzed using the separation theorem. After that, a cross-coupled controller is used to further improve the contour-tracking performance. Finally, simulations and experiments are carried out to verify the feasibility and effectiveness of the new approach.

Contour Tracking Control Based on Extended State Observer for Multiaxis Motion System

In the contouring process, the trajectory generated by the computer numerical control (CNC) machine tool is a result of the multiaxis coordinated motion. The contour error has a direct impact on the accuracy of the machined product. To obtain higher contouring accuracy of the multiaxis motion control system, this paper presents a cross-coupled control approach based on the extended state observer sliding mode control. First, a single-axis sliding mode controller is designed, and an extended state observer is used to estimate system disturbances and improve the system robustness. Then, the cross-coupled control approach handles the coordinated motion of multiple axes to improve the contour control accuracy. Next, a simulation study is conducted on the three-axis motion platform. Its result shows that the control algorithm is effective in reducing tracking errors and contour errors.

Improving Contouring Accuracy by Using Gain Matching Method

Motion axes should coordinate exactly in order to get high contouring accuracy. Gain matching is one of the coordinating problems. In this paper, gain matching effects on contouring accuracy are analyzed for both full-closed and half-closed control loop structures. A simple gain matching model is proposed in order to reduce the contouring error caused by unmatched gains of a multi-axis motion control system. According to this model, the contouring error can be reduced by tuning the proportional gain in the position loop of each axis. Finally, experiments are made to verify the proposed model, and the results show that the gain matching model can effectively reduce the contouring error of both linear and circular trajectory of motion control systems.

Contouring error modeling and simulation of a four-axis motion control system

A layered modeling method is proposed to resolve the problems resulting from the complexity of the error model of a multi-axis motion control system. In this model, a low level layer can be used as a virtual axis by the high level layer. The first advantage of this model is that the complex error model of a four-axis motion control system can be divided into several simple layers and each layer has different coupling strength to match the real control system. The second advantage lies in the fact that the controller in each layer can be designed specifically for a certain purpose. In this research, a three-layered cross coupling scheme in a four-axis motion control system is proposed to compensate the contouring error of the motion control system. Simulation results show that the maximum contouring error is reduced from 0.208 mm to 0.022 mm and the integration of absolute error is reduced from 0.108 mm to 0.015 mm, which are respectively better than 0.027 mm and 0.037 mm by the traditional method. And in the bottom layer the proposed method also has remarkable ability to achieve high contouring accuracy.

Data Interchange Mechanism in Multi-axis Ultra-precise Synchronous Motion Control System

Multi-axis ultra-precise synchronous motion control system needs to adopt parallel multiprocessors architecture. A data interchange mechanism based on distributed shared memory to realize high-efficiency data sampling and transmission in this type of control system is proposed. Multi-bus motion control network involving user-defined internal bus is designed, which constructs globally unified addressing memory model based on distributed local memory. Hardware-implemented message passing service refreshes shared data to ensure data consistency, which actually minimizes memory access time. Pipelined execution of data interchange and real-time control optimizes the slot allocation in parallel computing cycle, which maximizes the efficiency of parallel-processors. Precise synchronization strategy in data interchange realizes synchronous sampling of laser measuring position datum. Experimental results show the performances of data interchange mechanism not affected by increasing number of processors can realize stable bandwidth and precise transmission latency. Sub-nanosecond scaled synchronous position sampling can be implemented, and synchronization error has stable distribution characteristics towards transmission distance. The validity of this research has been proved in actual application.

Research on Distributed Multi-Axis Motion Control System Based on CANopen

The 32-bit ARM Cortex-M3 core processor Stm32f107vc which integrates two sets of bxCAN interfaces is used as hardware platform to achieve the design of hardware module and software module in this paper. Firstly, real-time multi-tasking operating system μCOS-II is ported to stm32 processor, then open source protocol stack microCANopen which is high real-time and reliable is transplanted under the μCOS-II, so a design of CANopen slave station is achieved. The CAN analyzer which is equipped with monitor trace functionality is used as CANopen master station to start the network, with three CANopen slave stations and one HMI, a distributed multi-axis motion control system based on CANopen which achieves network management and synchronous transmission of data in distributed control system is designed. On above basis, Fuji ALPHA5 Smart servo is used as executive member, modular design of reconfigurable motion control algorithm is realized, furthermore, The flexible module configuration enables the designer to develop systems conveniently according to the change of control requirement and network topology. This distributed control system not only has good real-time performance and stability, but also can reduce the complexity, enhance the flexibility of control system and save cost.

Design and Implementation of a Delay-Guaranteed Motor Drive for Precision Motion Control

This paper proposes a systematic design approach for a precision-guaranteed motion control system. We develop a delay-guaranteed motor drive with our new software implementation and real-time Ethernet, which can be used as a building block to build up a multi-axis motion control system. Our drive software implementation provides a probabilistic guarantee on drive-local processing delays to motor actuation, while real-time Ethernet provides a deterministic guarantee on message communication delays from a motion control host to each drive. In the paper, we address the precision of a motion control system in two terms: host cycle time and simultaneous actuation deviation. The host cycle time is a period with which the host can periodically release motor control messages while the average drive utilization does not exceed 1, and the simultaneous actuation deviation is the difference between the earliest and the latest actuation at different drives in response to the same message. In our approach, the main objective is to minimize the periods of tasks in each drive, using our stochastic analysis, which gives us a minimum possible host cycle time. Together with an existing delay analysis of real-time Ethernet, we analyze the end-to-end delay from message release to motor actuation and in turn the simultaneous actuation deviation. Through experiments, we show that for various requirements on the deadline miss probabilities of the tasks, we can successfully reduce the host cycle time and evaluate the resulting distribution of the simultaneous actuation deviation depending on the number of drives.

Design of Multi-Axis Motion Controlled System Based on SERCOS Bus

SERCOS is an international standard for communication in the digital servo system and electrical drives. It has been increasingly used in industrial automation equipment. This paper introduces the working principle and property of the SERCOS interface, and the SERCOS bus technology is used in the multi-axis motion control system. The PC coordinately control the slave computer through SERCOS bus. At the same time, PC will receive the feedback information of motion parameters timely, which can enhance the flexibility of the control system. SERCOS realizes the multi-axis motion based on the TwinCAT software platform, which has verified the rationality and feasibility of the control structure.

Design of Interpolation Algorithm in the Multi-Axis Motion Control System

This paper describes an interpolation algorithm in the multi-axis motion control system, which can achieve six-axis interpolation operations, greatly improving the processing efficiency. Using modular design idea on the Quartus II platform, by DDA interpolation theory, interpolation modules are built through VHDL. And these interpolator modules are connected into schematic diagrams. By those schematic diagrams a linear interpolator, a circular interpolator and a composite interpolator are formed. The corresponding functions of those interpolators have been simulated on the Quartus II platform. The simulation shows that this interpolation algorithm is effective to complex multi-axis motion control system.

Study on the Multi-Axis Motion Control System Based on Ether CAT

Now, the complication and systemization of the industry is increasing day after day, which make it hard to design the motion control system. However, the technology of field control is increasing, and the motion control system based on the network is widely used. The company of beck Hoff introduced the Ether CAT network, which can be configured easily, and the speed of communication is high, and in some way, the technology has become the focus of the studying the automation. This paper analyst the application for the Ether CAT in the multi-axis motion control system.

Motion Control System using SERCOS over EtherCAT

SERCOS interface (SErial Real time COmmunication Specification) is known as a universal ‘motion control’ interface, while EtherCAT (Ethernet for Control and Automation Technology) is a high-speed, real-time, topology-flexible industrial ethernet for data communication in process automation and factory automation control system. In order to implement the SERCOS interface on the EtherCAT network, a SERCOS over EtherCAT (SoE) model is used in this paper. By introducing statemachine mapping and data mapping method, the SERCOS statemachine, service channel, IDNs and all kinds of telegram can be supported by EtherCAT. Simultaneously, EtherCAT is accessible to the servo profiles and drive parameters defined by SERCOS. The SoE model ensures the transmission of real-time motion control data in a maximum speed. For illustration, a high speed multi-axis SoE motion control system is developped which operates the highly synchronized movement with multi-servo drivers. The system which combines SERCOS interface with the advantages of Ethernet structure shows the outstanding real-time behavior. This paper provides a kind of brand-new control plan for the numerical control equipment and industrial robots.

Design of a Distributed Multiaxis Motion Control System Using the IEEE-1394 Bus

This paper presents a distributed multiaxis motion control system based on the IEEE-1394 bus. In the system design, the Unified Modeling Language is employed to illustrate interactions of the objects required in the system. The developed system consists of a set of smart distributed control nodes connected one by one through the IEEE-1394 bus. Each smart node contains four modules, i.e., an IEEE-1394 interface module, a digital signal processor module, a field-programmable gate array module, and a digital-to-analog converter module. It accomplishes its own control task and coordinates with the others through information exchanges, sampling sensor signals, and controlling actuators. A scheduled communication protocol is proposed according to the criteria in terms of bounded time delay and guaranteed transmission. Time delays arising from data processing and message transmission are analyzed. A platform is built, and experiments are conducted to demonstrate the capabilities of the developed distributed control system for real-time communication and synchronous tracking control, which are required for multiaxis applications. The results verify the feasible application of the IEEE-1394 bus to distributed motion control.