Networked Motion Control System Research Articles

Performance guaranteed attack reconstruction for cyber–physical systems: A new intermediate estimator-based framework

For attack reconstruction issue of cyber–physical systems (CPSs), it is a challenge to guarantee online computational efficiency and reconstruction accuracy simultaneously, especially for cases with actuator attacks. However, most existing approaches are only focused on sensor attacks. This brief paper studies the multiple attack reconstruction problem for CPSs. A new projected intermediate estimator is proposed, where the computation complexity problem is solved by reducing the number of loop iterations significantly via enhancing the designs of loop iteration, termination condition and parameter selection strategy, without sacrificing the attack reconstruction performance. Compared with traditional intermediate estimators, the dependence of linear matrix inequality technique is completely removed, besides, the intrinsic heavy overshooting problem in transient period is effectively alleviated. The application to a networked motion control system verifies the effectiveness and superiority of the presented method.

Networked Motion Control for Smart EV With Multiple-Package Transmissions and Time-Varying Network-Induced Delays

This article aims to address the coupled problem of the multiple-package transmissions (MPT) and time-varying network-induced delays (TND) within the networked motion control systems of smart electric vehicles (EVs). The recent development of advance digital sensors, actuators, and controllers leverage the worldwide upgrade of transportation in terms of electrification and intellectualization. However, for smart EVs, this updating may challenge the in-vehicle network and then the vehicle control performance. In particular, the nonsynchronous MPT and the TND are the key issues in the vehicle's integrated motion control due to the absence of the synchronization mechanism and limitation of communication bandwidth. To deal with the effects of coupled MPT and TND, a hybrid schedule-control framework is developed, where a new MPT scheduler is developed with a flexible time-triggered schedule strategy with fractional-type basic period to eliminate the effect of the MPT and reorganize the TND to a bounded range of delay. Furthermore, an H∞-based linear quadratic regulator control approach is designed to deal with the uncertainties caused by the TND as well as guarantee the system's stability. The effectiveness of the proposed scheme is verified in three cases by the real-time hardware-in-the-loop bed tests.

Secure Teleoperation Control Using Somewhat Homomorphic Encryption

The goal of this research is to establish control theoretic methods to enhance cyber security of networked motion control systems by utilizing somewhat homomorphic encryption. The proposed approach will encrypt the entire motion control schemes including: sensor signals, model parameters, feedback gains, and performs computation in the ciphertext space to generate motion commands to servo systems without a security hole. The paper will discuss implementation of encrypted bilateral teleoperation control schemes with nonlinear friction compensation. The paper will present (1) encrypted teleoperation control realization with somewhat homomorphic encryption and (2) simulation results.

Dynamic Network Path Provisioning and Selection for the Detection and Mitigation of Data Tampering Attacks in Networked Control Systems

Networked control systems can help build cost-effective and flexible industrial systems. A system that can function while being immune to cyberattacks is necessary. A method called fixed redundant path selection (FRPS) has been proposed to detect and mitigate data tampering attacks in a networked motion control system. This system contains redundant forward network paths from the controller to the motor sides to detect the attacked path by comparing the values that are received through respective paths. Then, a path selector on the motor side chooses a value on the path that is not attacked based on the majority decision. Increasing the number of redundant paths improves the detection performance of simultaneous attacks against multiple paths. However, it also increases the amount of traffic because the same data are transmitted to all of the redundant paths. This study proposes a dynamic redundant path selection (DRPS) method to balance the detection performance and the amount of traffic. The proposed method initially applies three redundant paths and changes the number of redundant paths to five only when the path selector detects a difference among the received values for the three paths. The experiments confirm that the proposed DRPS outperforms the conventional FRPS. The former can detect and mitigate the data tampering attacks while reducing the number of network paths during tampering detection when the system is exposed to simultaneous attacks against up to two of the redundant paths.

Sensor attack detection for cyber‐physical systems based on frequency domain partition

This study is concerned with the attack detection (AD) problems in finite frequency domain for cyber-physical systems with sensor attack. The frequency domain is divided into three frequency domains of low, medium and high, multiple AD filters are designed to work simultaneously. The attack detectionAD problem is transformed into a multi-objective optimisation schemes for each finite frequency domain. Finally, the experimental results of networked motion control system are given to verify the effectiveness and superiority of proposed method.

High-Precision Contour-Tracking Control of Ethernet-Based Networked Motion Control Systems

High-Precision Contour-Tracking Control of Ethernet-Based Networked Motion Control Systems

A GESO based MPC approach to contour error control of networked motion control system

This paper presents a generalised extended state observer (GESO) based model predictive control (MPC) approach to contour error control for networked multi-axis motion system (NMAMS) with network-induced delays. First, the uncertainties induced by the network-induced delays are modelled as an additive bounded disturbance, and a novel model predictive controller based on the GESO is designed for the uniaxial trajectory tracking control system. The GESO is used to estimate the system state and the disturbance simultaneously, and the effects of the uncertainties induced by the delays are eliminated by the proposed GESO based controller. Then the contour error estimation method is adopted, and a PID controller is designed to compensate the contour error. Finally, experiments are carried out to demonstrate the effectiveness of the proposed method.

A LADRC based fuzzy PID approach to contour error control of networked motion control system with time‐varying delays

AbstractThis paper investigate the contour error control problem for networked multi‐axis motion system (NMAMS) with time‐varying delays. Firstly, the uncertainties induced by the delays are modeled as a part of the total disturbance, and a linear active disturbance rejection controller (LADRC) is designed for the uniaxial trajectory tracking control. In the LADRC, a linear extended state observer (LESO) is designed to estimate the system state and the total disturbance simultaneously, and the effect of the total disturbance is eliminated by the designed linear feedback error control law. Then, the classical contour error estimation method is adopted, and a fuzzy PID controller is designed to compensate the contour error to achieve a better contour tracking performance. Finally, experiments are provided to verify the effectiveness of the proposed method.

Implementation of Network Motion Systemusing RTEX Network for XY Gantry

Recently, the weapon systems are more and more complex and the demands for handling and maintaining these complex systems effectively are increased. For this reason, industrial control network had been developed for many years and the needs for the development of a totally networked automation environment are raised. To meet these requirements, networked motion control systems tend more and more to replace the traditional solutions. In this paper, the XY platform motion control system employing RTEX (Real Time Express) network which is one of the Ethernet based vender-oriented industrial networks is tackled. The network motion controller which generates motion profile and outputs the pulse train is implemented and is applied to XY platform. As results, it is shown that the proposed network motion controller works properly to control the XY platform and monitors the system easily through network.

Research and realisation of real-time Ethernet protocol for networked motion control system

Existing control cards typically use non-real-time Ethernet protocols, such as TCP/IP, making it difficult to achieve multi-axis synchronisation between control cards. A practical scheme is proposed in this paper to solve this problem. In this scheme, the internal clocks of control cards are adjusted to the same value by the sync frames periodically sent by the host. The jitter of the sync frame has very little impact on the consistency of the clocks of all control cards. This alleviates the real-time performance requirements of the host, and thus reduces the cost and design difficulty. In addition, all synchronous or asynchronous frames are unified into a cluster frame model, which simplifies the processing of the frames, making it easy to implement in hardware such as FPGAs. This real-time Ethernet protocol has been implemented in a large-scale motion control chip. And the test results showed that this scheme achieves expected performance.

Research and realisation of real-time Ethernet protocol for networked motion control system

Existing control cards typically use non-real-time Ethernet protocols, such as TCP/IP, making it difficult to achieve multi-axis synchronisation between control cards. A practical scheme is propose...

A Double Disturbance Observer Design for Compensation of Unknown Time Delay in a Wireless Motion Control System

Unknown time delay poses a significant challenge to the design of networked motion control systems. Moreover, modeling uncertainties, mechanical disturbance, and sensor noise coexist with time delay in such systems, which makes the controller synthesis even more challenging. It has been proven effective to model the time delay as fictitious disturbance so that a disturbance observer (DOB) can be employed to cancel the negative effect of time delay. In this brief, a new double DOB (DDOB) design is proposed by adding one more DOB into the control system to handle actual external disturbance and enable satisfactory tracking performance. Design considerations of the baseline controller and the two DOBs are illustrated, and robust stability analysis is provided to handle modeling uncertainties. A real-time wireless communication protocol, RT-WiFi, is integrated with a DC motor to examine the performance of the proposed DDOB by simulations and experiments.

Frequency-Tracking Clock Servo for Time Synchronization in Networked Motion Control Systems

With the application of internet in manufacturing, motion control system is tend to networking. Clock synchronization is a basic requirement to guarantee capability of coordination in networked motion control systems. In this paper, we propose a frequency-tracking clock servo (FTCS) to adjust the local clock to synchronize with the reference clock. The frequency of FTCS can rapidly lock onto the reference frequency and the offset can be fully compensated within a single synchronizing cycle. Simulations and experiments are performed to validate the feasibility and superiority of FTCS. Compared with the proportional-integral clock servo, FTCS can achieve the rapid synchronized speed and better precision with low frequency of sending synchronization messages.

Comparative Analysis of a Selected DCT-Based Compression Scheme for Haptic Data Transmission

In this study, a novel compression and decompression algorithm, namely the selected discrete cosine transform (DCT), is presented for implementation in networked motion control systems. The proposed method relies on the utilization of a selection algorithm based on bubble sorting to choose the highest power coefficients of the signal obtained by using DCT. In order to better illustrate the effectiveness of the proposed method, comparisons are made with the methods existing in the literature. To this aim, the basics of the compression schemes used in the comparison, namely, the DCT, discrete Fourier transform, and wavelet packet transform, are also briefly discussed followed by the derivation of the proposed method. The algorithmic bases of all four schemes are given to provide further reference for practical applications. The proposed method is tested on an experimental platform consisting of a single-single-degree-of-freedom master and slave systems, and the results are comparatively analyzed based on relevant performance evaluation metrics. The obtained results demonstrate the improvement achieved by the proposed compression scheme over the existing compression methods used in network-based motion control applications, hence proving the feasibility of the approach in teleoperation systems.

Fuzzy Speed Control of Networked Motion Control Systems

This paper proposed an integrated scheme for the modeling and control of induction motors in the networked environment. The networked control system (NCS) is built in hierarchical structure, which consists of a networked speed controller and a local controller. In the networked speed controller, fuzzy gain scheduling is applied to guarantee the robustness against communication constraints. Furthermore, a state predictor is designed to compensate the time delay occurred in data transmission from the sensor to the controller, as a component of the networked speed controller. Simulation and experimental results are given to illustrate the effectiveness of the proposed approach.

Guaranteeing Isochronous Control of Networked Motion Control Systems Using Phase Offset Adjustment.

Guaranteeing isochronous transfer of control commands is an essential function for networked motion control systems. The adoption of real-time Ethernet (RTE) technologies may be profitable in guaranteeing deterministic transfer of control messages. However, unpredictable behavior of software in the motion controller often results in unexpectedly large deviation in control message transmission intervals, and thus leads to imprecise motion. This paper presents a simple and efficient heuristic to guarantee the end-to-end isochronous control with very small jitter. The key idea of our approach is to adjust the phase offset of control message transmission time in the motion controller by investigating the behavior of motion control task. In realizing the idea, we performed a pre-runtime analysis to determine a safe and reliable phase offset and applied the phase offset to the runtime code of motion controller by customizing an open-source based integrated development environment (IDE). We also constructed an EtherCAT-based motion control system testbed and performed extensive experiments on the testbed to verify the effectiveness of our approach. The experimental results show that our heuristic is highly effective even for low-end embedded controller implemented in open-source software components under various configurations of control period and the number of motor drives.

Design Approach Based on EtherCAT Protocol for a Networked Motion Control System

This paper presents a new design approach based on EtherCAT protocol aiming at a special networked motion control system. To evaluate this system, the testing platform of the networked motion control system for ocean wave maker is designed. The paper gives the detailed design for the testing platform including software and hardware. With message access delay and jitter, a set of experiments are done to evaluate the crucial performance for the implemented networked motion control system. By analyzing the experimental results, the systemic performance is verified. And the design approach can be widely extended to other automation application scenarios.

Formal Modeling and Verification of Motor Drive Software for Networked Motion Control Systems

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Design and Performance Evaluation for a Class of Networked Motion Control System

Design and Performance Evaluation for a Class of Networked Motion Control System

Implementing for Networked Motion Control System with Large-Capacity Data Acquisition

As one of the most popular real-time Industry Ethernet protocols, EherCAT has become widely used in distributed networked motion control systems. By the help of the unique features, the EtherCAT protocol is adopted to construct a networked servo motion control system with low delivery delay and high accurate clock synchronization in the paper. This system can achieve not only high-speed synchronous transmission of motion control commands and feedback information but also high-efficiency large-capacity data acquisition with low delay and jitter. A set of experiments, which evaluate the crucial performance for the implemented networked motion control system including messages access delay and jitter, are performed. Through analyzing the experimental results, the system performance is verified.