Communication Disturbance Observer Research Articles

Simultaneous Time-Delay and Data-Loss Compensation for Networked Control Systems With Energy-Efficient Network Interfaces

Networked control systems (NCSs), in which controllers and actuators are connected by communication networks, have been utilized in both industrial and consumer applications. In addition, sleep-based energy-efficient network interfaces have been developed for constructing a green networked society. The combination of the NCSs and energy-efficient network interfaces is a promising approach to reduce the power consumption of NCSs. However, sleeping of the network interface results in loss of data to be transmitted between a controller and an actuator. The sleep-induced data loss causes degradation of control performance. Moreover, NCSs originally include network delay for both forward and feedback paths, which also degrades control performance. This paper proposes a time-delay and data-loss compensation method using a modified communication disturbance observer (MCDOB) for NCSs with sleep-based energy-efficient interfaces. The proposed MCDOB can simultaneously compensate for not only the network delay but also sleep-induced data loss as a disturbance, whereas a conventional communication disturbance observer (CDOB) considers only network delay or network-induced data loss and cannot be directly introduced into the NCSs with sleep-based energy-efficient interfaces. Experimental results show that the proposed method with MCDOB outperforms the conventional method without the MCDOB in terms of integral square error (ISE) and communication rate, which indicates the power consumption of network interfaces.

Piecewise Continuous -Communication Disturbance Observer Design for Networked Visual Servo Control Systems with Sampled and Variable Delayed Output

The paper deals with the state estimation of networked visual servo control systems (NVSCS) using sampled and delayed output measurements. A continuous state observer is proposed which makes possible to estimate the NVSCS state in the case of fixed sampling period and variable and bounded time delay. The stability of the new state observer is studied in detail. The performances of the proposed observer are compared by numerical simulations with those of the Lyapunov–Krasovskii state observer.DOI: http://dx.doi.org/10.5755/j01.itc.47.4.19872

Compensation of time delay effect in vehicle yaw stability control systems by using communication disturbance observer

Compensation of time delay effect in vehicle yaw stability control systems by using communication disturbance observer

Robustness improvement of DC motor speed control using communication disturbance observer under uncertain time delay

The speed control problem of a time-delay DC motor system is proposed because the control performance can severely deteriorate under uncertain delay time information. Since most of existing delay compensators require exact system parameters and delay time information, the performance improvement has been limited under delay time uncertainty. The proposed method incorporates a disturbance observer on the slave side of the system with a communication disturbance observer that does not require the delay time information for generating a predicted output signal. The effectiveness of the proposed algorithm is tested through comparative simulations and experiments using a testbed system under large delay time uncertainty.

Design and implementation of a modified communication disturbance observer for teleoperation systems

In this paper, a novel structure for a communication disturbance observer in teleoperation systems is proposed to achieve robust stability. A time delay compensation method based on the concept of network disturbance and a communication disturbance observer (CDOB) has been proposed in past research. Unlike model-based approaches, it works without a time delay model. Therefore, it can be implemented in teleoperation systems with unknown and time-varying delay. However, it has been observed that the system model errors and external disturbances seriously affect the steady-state characteristics. Hence, in this paper, to achieve robustness against disturbance and model uncertainty, the structure of the conventional CDOB is modified and a new structure for the CDOB in teleoperation systems is proposed, which uses the slave's delayed torque instead of its delayed position for time delay compensation. The desired transient response characteristic is achieved by designing the controller parameters. The time delay in the communication channel has been simulated by PCs in past studies, but in this paper, by implementing the communication channel through the TCP/IP protocol in the experimental setup, the effectiveness of the proposed structure is studied in the presence of real time delay and compared with the Smith predictor, the conventional CDOB, and other structures of CDOBs.

Full FPGA Tracking Control System Based on Error-Based Communication Disturbance Observer Considering Time Delay for Optical Disc System

Full FPGA Tracking Control System Based on Error-Based Communication Disturbance Observer Considering Time Delay for Optical Disc System

Delay Compensation for Teleoperation Systems Based on Communication Disturbance Observers

This paper investigates the control problem for a class of teleoperation systems with communication delays. The network-induced delays are usually inevitable in teleoperation systems, and may be time varying and unpredictable. Since the conventional Smith predictor is only useful for fixed delays, a novel delay compensation and controller design method is proposed in this paper. The proposed method combines a disturbance rejection controller and a communication disturbance observer (CDOB). Simulations are provided to show the effectiveness and superiority of the proposed delay compensation and controller design method.

Development of a four-channel haptic system for remote assessment of patients with impaired hands

SUMMARYHaptic devices have proven effective in stimulating proprioceptive sensing in post-stroke patients. In this work, pre-existing devices were used together in a remote environment for the teleassessment of impaired hands. A four-channel bilateral control system in the presence of large and variable time delay is proposed as a proof of concept. Time delay is managed with a novel communication disturbance observer (CDOB). The system also employed a scaling down compensation value (SDCV) for the CDOB. The proposed control system was tested successfully in bilateral haptic interaction, simulating a remote motor and functional evaluation of patients' hands, guaranteeing safe and stable interaction, even in the presence of large network delays.

Model-Error Feedback for Systems with Time-Varying Delay Based on Mixed <i>H</i><sub>2</sub>/<i>H</i><sub>∞</sub> Control

This paper proposes a method that uses model-error feedback to improve the steady-state performance of a communication disturbance observer (CDOB) and a controller design based on the stability theorem with a Lyapunov-Krasovskii functional. The conventional CDOB faces the problem of a steady-state error due to model error, and the stability of a system with time-varying delay is not guaranteed. To solve the issue, the controller based on the mixed H2/H∞ control problem is introduced. The paper presents a solution that uses a controller design based on the Lyapunov stability theorem and model error feedback.

Experimental validation of communication disturbance observer for networked control systems with information losses

Experimental validation of communication disturbance observer for networked control systems with information losses

Method of Time‐Delay Compensation in Multi‐Degree‐of‐Freedom Bilateral Control Systems with Different Configurations

SUMMARYIn this paper, a time‐delay compensation method based on a work space communication disturbance observer (WCDOB) is proposed. Time delay degrades the stability of a control system. A communication disturbance observer (CDOB) has been proposed to solve this problem. However, CDOB cannot compensate for time delay in multi‐degree‐of‐freedom bilateral control systems with different configurations, because the inertia of the robots is not fixed. In contrast, WCDOB can estimate the time delay based on work space information and compensate for them. The experimental results confirm the validity of the proposed method.

不安定な通信ネットワークを考慮した通信外乱オブザーバ内の制御対象モデルの配置方法

Time delay problem used to be dealt mainly in process or plant engineering in the early phase of time delay systems research. In recent years, time delay problem in network-based control systems has been attracting much attention. This kind of network is usually unstable, and time delay is time varying and unpredictable. As a time delay compensation method, Smith predictor was a famous and useful approach. However, this method uses time delay model to compensate for time delay effect and so it is not a practical method for network-based control systems. Thus, communication disturbance observer (CDOB) has been proposed to compensate for time delay effect without using a time delay model. However, a large steady state error occurs, if the network is unstable. This paper modifies the structure of a time-delayed control system with CDOB considering an unstable network. To reduce nonlinear effects such as jitter or packet dropouts, the allocation of the system model in the CDOB has been modified. Then, the robustness of the modified CDOB structure against packet dropouts and jitter is confirmed by simulation. The validity of the modified structure is shown by experimental results.

通信外乱オブザーバにおけるモデル誤差を補償した時間遅れシステムの設計

通信外乱オブザーバにおけるモデル誤差を補償した時間遅れシステムの設計

Digital Control of PWM Inverter Using Ultrahigh-Speed Network for Feedback Signals with Communication Disturbance Observer Based on Rocket I/O Protocol

Digital Control of PWM Inverter Using Ultrahigh-Speed Network for Feedback Signals with Communication Disturbance Observer Based on Rocket I/O Protocol

Improvement in Steady-State Accuracy of Time-Delayed Control Systems with Communication Disturbance Observer by Low-Frequency Model Error Feedback

This paper proposes a method to improve the steady-state accuracy of time-delayed control systems with a communication disturbance observer (CDOB) by low-frequency model error feedback. The advantageous feature of time delay compensation by the CDOB is that it can be utilized without a delay time model. However, the CDOB needs a model of controlled system, and the model error occurs as the steady-state error. To solve this problem, this paper proposes model error feedback only in the low-frequency area. The proposed method achieves both high robust stability and steady state accuracy.

Compensation of Time Delay in a Network-based Gait Rehabilitation System with a Discrete-time Communication Disturbance Observer

In this paper, a network-based gait rehabilitation system is proposed for enhanced mobility and tele-rehabilitation. In the proposed rehabilitation system, a compact rotary elastic actuator (cRSEA) is employed to provide assistive torque to the patients and it is controlled over a local wireless network. However, time delay exists in both sensor-controller and controller-actuator channels, which leads to performance degradation and even destabilization. Moreover, the amount of time delay is time-varying and it is difficult to measure accurately. In order to compensate the time delay and guarantee stability of the system, a communication disturbance observer (CDOB) is designed in the discrete-time domain. Parameters are tuned based on the linear quadratic regulator (LQR) design technique and compared to other parameter choices in the frequency domain in terms of closed-loop stability, tracking performance, disturbance attenuation, and noise cancellation. Simulation and experimental results are shown to validate the performance of the proposed controller.

通信外乱オブザーバを用いた通信遅延下におけるバイラテラル遠隔操作の適応的性能調整手法

通信外乱オブザーバを用いた通信遅延下におけるバイラテラル遠隔操作の適応的性能調整手法

Time-Delay Compensation by Communication Disturbance Observer for Bilateral Teleoperation Under Time-Varying Delay

This paper presents the effectiveness of a time-delay compensation method based on the concept of network disturbance and communication disturbance observer for bilateral teleoperation systems under time-varying delay. The most efficient feature of the compensation method is that it works without time-delay models (model-based time-delay compensation approaches like Smith predictor usually need time-delay models). Therefore, the method is expected to be widely applied to network-based control systems, in which time delay is usually unknown and time varying. In this paper, the validity of the time-delay compensation method in the cases of both constant delay and time-varying delay is verified by experimental results compared with Smith predictor.

Bilateral teleoperation under time‐varying communication time delay considering contact with environment

AbstractWith recent popularization of the Internet, bilateral control systems which are robust to fluctuant and unpredictable time delay are desirable. In such a situation, communication disturbance observer (CDOB) has been proposed as a control method for fluctuant and unpredictable time delay in bilateral teleoperation. It compensates time delay using disturbance observer by considering the effect of communication delay on the system as acceleration dimensional disturbance. Since this method cannot separate network disturbance from contact force exerted on a slave, force response of the slave transmitted to the master side is not precise. This paper presents a method for separating network disturbance from the contact force exerted on the slave. By producing the compensation value using separated network disturbance the force response value of the slave is transmitted to the master side more precisely. The validity of the proposed method is verified by experimental results. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(7): 38–46, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10051

Stability Analysis and Practical Design Procedure of Time Delayed Control Systems With Communication Disturbance Observer

In a research field of network-based control systems (NBCSs), the time delay problem is one of the most significant issues. Efficient stabilization methods of time delayed control systems enable NBCSs to be flexibly applied to many kinds of situations. A novel time delay compensation method based on the concept of network disturbance (ND) and communication disturbance observer (CDOB) has been proposed. The compensation method has the same effectiveness as that of the Smith predictor. In addition, since the method is simple and does not need time delay model or time delay measurement, it can be easily implemented to various applications. However, the design method has not been concerned so far. This paper therefore presents stability analysis and studies a practical design procedure of the time delayed control systems with CDOB. At first, the concept of ND is introduced and the validity of the time delay compensation method is described. Then an analysis about the effects of parameters in control systems on stability is conducted. Characteristics of the effects of parameters on stability come out. Then we study a practical design procedure of the time delayed control systems. The validity of the design procedure is validated by experimental results. In the experiment, we also verify the performance of the system in the case of time-varying delay. Finally, comparative study of the method to the Smith predictor is presented.