Anti‐Sway Crane Control Considering Wind Disturbance and Container Mass

A method for estimating the sway angle using an observer has already been proposed. The state observer estimates the sway angle accurately and must use the detected sway angle value. However, the estimated sway angle has an error owing to rope length error, friction force, and wind. Moreover, the container mass cannot be determined, and therefore the observer parameter is not suitable. We already proposed robust antisway control for overcoming rope length error without adding a new sensor. Further, we designed a friction disturbance observer to cancel out the influence of the friction force. In this paper, we first propose a container mass estimation method when a crane system performs rolling up control. The observer parameter can be selected using the estimated mass value. Second, in crane parallel shift control, we propose a robust antisway control even when there is a wind disturbance. We design a wind disturbance observer and propose a wind disturbance estimator to separate the friction observer output from the wind disturbance observer output. We confirm through experiments that the proposed method can reduce vibration.     

Two‐Degree‐of‐Freedom Robust Temperature Control of Peltier Device Based on Heat Disturbance Observer

Recently, the Peltier device has been attracting attention as a haptic device that can transfer heat, because it has relatively fast response characteristics among thermal devices. To transmit thermal sensation, temperature control is considered to be important. However, it is difficult to design a controller because of factors such as parameter variations, nonlinear characteristics of the device, and heat that flows from an external object. Furthermore, it is preferable that the tracking performance and disturbance suppression characteristics be designed independently. To address these factors, this paper proposes a heat disturbance observer, which is constructed by using the disturbance observer commonly used in the field of motion control. When the observer is used, the thermal system becomes robust to the above‐mentioned factors. In addition, it is possible to design the tracking performance independently of the disturbance suppression characteristics. The validity of the proposal is confirmed by experimental results. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 184(1): 66–74, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22282     

High‐precision positioning of table drive system using strain feedback and disturbance observer

This paper presents a control design methodology for high‐precision positioning. In particular, the compensation for the effects of vibration modes and nonlinear friction on the positioning performance is taken into account in this methodology. In the controller design, the servo bandwidth of the feedback control loop should be expanded to compensate for nonlinear friction, while robust stability with respect to frequency variations in the vibration modes should be ensured. In this study, therefore, strain feedback for vibration modes is adopted to provide robustness with respect to frequency variations and to improve the disturbance suppression performance by expanding the bandwidth of a disturbance observer. This strain feedback is based on the use of a piezoelectric element. The efficiency of the proposed positioning control approach has been verified by conducting experiments using a prototype for industrial table drive systems. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(3): 46–55, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21306     

Vibration control of flexible arm by multiple observer structure

This paper describes vibration control of a flexible arm by multiple‐observer structure using the accelerations of the arm. In general, a flexible arm has several oscillation modes. In the model of a flexible arm described as a two‐mass resonant system, the reaction torque feedback makes the flexible arm system stable. In the N‐mass resonant system, it is known that the reaction torque feedback makes all oscillation modes, only the reaction torque feedback is not enough to make the system stable. Resonance ratio control with the arm disturbance observer has been proposed. The arm disturbance observer is able to suppress the disturbance applied to the tip, but it is not sufficient for the disturbance applied to other points on the arm. The aim is to make the control system robust to arm inertia variation and disturbance. This paper proposes vibration control of flexible arm by acceleration feedback, and disturbance rejection by multiple‐observer structure using the acceleration of the arm. The validity of the proposed method is shown by simulations and experiments. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 154(2): 68–75, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20175     

Composite adaptive disturbance observer‐based control for a class of nonlinear systems with multisource disturbance

Antidisturbance control and estimation problem are introduced for a class of nonlinear system subject to multisource disturbances. The uncertain multisource disturbances consist of not only a single harmonic or constant disturbance but also another unexpected nonlinear signal described as a nonlinear function. The composite adaptive disturbance observers are constructed separately from the controller design to estimate the disturbance with partial known information. By integrating disturbance observer‐based controller with robust adaptive control, a novel type of composite adaptive disturbance observer‐based control scheme is presented for a class of nonlinear system with multisource disturbances. Simulations for a flight control system are given to demonstrate the effectiveness of the results compared with the previous schemes. Copyright © 2012 John Wiley & Sons, Ltd.     

数字控制时延对扰动观测器性能的影响

数字控制中时间延迟问题会给系统的性能造成一定的影响。文章将分析带有扰动观测器的伺服系统户时间延迟对系统稳定性、鲁棒性以及抗扰动性能的影响。     

A study on higher‐order disturbance observer and robust stability

In earlier papers, it has been reported that a fast and precise servo system, which has low sensitivity to parameter variation and disturbance, can be realized with simple structure by using a high‐order disturbance observer. However, no clear and simple design method satisfying specifications for robust stability, the influence of measurement noise, and relative stability (damping characteristics) for large parameter variation has been proposed. In this paper, we clarify the class of robust servo systems realized by adjusting the order of the disturbance observer and the control parameters. We apply this strategy to the design of a second delay system, such as a position servo system, and realize a high‐performance robust servo system using a high‐order disturbance observer. © 1999 Scripta Technica, Electr Eng Jpn, 128(1): 37–44, 1999     

伺服系统滑模变结构扰动及瞬时转速观测器

本文提出了一种滑模观测顺,用于观测伺服系统负载扰动及瞬时转速,不仅可以减小传统的Ｍ／Ｔ法测量速度造成的时间延迟,改善伺服系统动脉性能,而且通过动态转矩补偿控制,提高系统抗负载扰动的能力,仿真结果验证了该方案的有效性。     

Improving transparency of bilateral control system by sliding mode assist disturbance observer

Transparency is an important indicator to evaluate the performance of a bilateral control system. Uncompensated disturbances in high frequency degrade the transparency in the traditional disturbance observer (DOB) based bilateral control. This paper analyzes the influence of the uncompensated disturbances, and proposes a sliding mode assist disturbance observer (SMADO) to solve the problem. The sliding mode technique helps the original DOB to estimate the disturbances in high frequency by making use of a rapid switching control value. The required switching gain is small in the proposal, which is good for alleviating the chattering. Moreover, to avoid conservative and arbitrary design of the switching gain, a reasonable benchmark is proposed by employing the estimation error between the original DOB and another parallel DOB with a different cutoff frequency. The validity of the proposal is confirmed by experiments. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Advanced motion control by multi‐sensor‐based disturbance observer

Motion control has been widely used in industry applications. One of the key technologies of motion control is a disturbance observer, which quarries a disturbance torque of a motion system and realizes a robust acceleration control. The disturbance observer can observe and suppress the disturbance torque within its bandwidth. Recent motion systems have begun to spread in society and are required to have the ability to make contact with the unknown environment. Such a haptic motion requires a much wider bandwidth. However, since the conventional disturbance observer attains the acceleration response by the second‐order derivative of position response, the bandwidth is limited because of the derivative noise. This paper proposes a novel structure of a disturbance observer. The proposed disturbance observer uses an acceleration sensor for enlargement of bandwidth. Generally, the bandwidth of an acceleration sensor is from 1 Hz to more than 1 kHz. To cover the DC range, the conventional position sensor‐based disturbance observer is integrated. Thus, the performance of the proposed multisensor based disturbance observer (MSDO) is superior to the conventional one. The MSDO is applied to position control (infinity stiffness) and force control (zero stiffness). The experimental results show the viability of the method proposed. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Construction of a control system for disturbance rejection using a dual observer

A well‐known control system which can reduce the adverse effects of disturbances is a disturbance observer. However, in many cases of mechanical systems, system disturbances which do not satisfy the matching condition may be imposed. Therefore, it may be difficult to reduce the adverse effects of the disturbances by the traditional disturbance observer. In this paper, a method of control system synthesis for disturbance rejection using a dual observer is proposed. This method is based on the zeroing induced by the disturbance localization problem. This problem may be solved by dividing the state space into observable subspace and unobservable subspace. As compared with an H_∞ controller based on perfect observation, the usefulness of the proposed control system for disturbance rejection is demonstrated by numerical simulations for a two‐mass spring system. © 2002 Scripta Technica, Electr Eng Jpn, 138(4): 50–60, 2002; DOI 10.1002/eej.1138     

An adaptive robust observer for velocity estimation in an electro‐hydraulic system

This paper proposes the design of an observer to estimate the velocity of an electro‐hydraulic system by using pressure measurements only. The difficulties involved in the design of an observer for such a system include the highly nonlinear system dynamics, severe parametric uncertainties such as large variation of inertial load and unmatched model uncertainties. In order to address these issues, a nonlinear model‐based adaptive robust observer is designed to estimate the velocity. The contributions of the proposed work is twofold. First, it introduces a novel coordinate transformation to reconstruct the velocity estimate. And second, from a structural viewpoint, the design has two important features: (i) an underlying robust filter structure, which can attenuate the effect of uncertain nonlinearities such as friction and disturbances on the velocity estimation, and (ii) an adaptation mechanism to reduce the extent of parametric uncertainties. Experimental results on the swing motion control of an electro‐hydraulic robot arm demonstrate the effectiveness of the proposed observer. Copyright © 2012 John Wiley & Sons, Ltd.     

Sliding mode control for a class of uncertain nonlinear system based on disturbance observer

In this paper, a sliding mode control (SMC) scheme is proposed for a class of nonlinear systems based on disturbance observers. For a nonlinear system, the disturbance that cannot be directly measured is estimated using a nonlinear disturbance observer. By choosing an appropriate nonlinear gain function, the disturbance observer can well approximate the unknown disturbance. Based on the output of the disturbance observer, an SMC scheme is presented for the nonlinear system, and the stability of the closed‐loop system is established using Lyapunov method. Finally, two simulation examples are presented to illustrate the features and the effectiveness of the proposed disturbance‐observer‐based SMC scheme. Copyright © 2009 John Wiley & Sons, Ltd.     

Control using joint torque sensor of robot arm with two‐inertia resonance: Comparison with control using state‐estimation observer

Most industrial robots are driven through reduction gears such as Harmonic Drives and RV gears. Due to the flexibility of the drive system, vibratory behavior occurs during operation. When flexibility is considered, the drive system of the robot joint can be modeled as a resonant mechanical system called a two‐inertia system. Conventionally, studies of two‐inertia system have discussed semiclosed‐loop control using only motor information and a state observer. On the other hand, joint torque sensing of robots has been studied in the harmonic drives that are widely used in robot joints. The joint torque sensor is becoming available with higher performance. In this paper, we consider the control of a robot arm having two‐inertia resonance by using the joint torque sensor. The performance of the torque sensor and that of the observer are compared. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(2): 75–84, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20226     

Achievement method of high‐speed response of error prediction tracking control for optical disk system

This paper proposes the new design method of error‐prediction control systems combining the ZPET control and the robust feedback control. The error‐prediction control system based on ZPET control can reduce the tracking error caused by periodic disturbances more efficiently than the conventional repetitive control technique. However, the proposed tracking servo system does not reduce the residual tracking error caused by the low‐pass filter of the feedforward compensation and by the long sampling time. In order to overcome this problem, this paper proposes the new structure of the feedforward tracking control system. The modified ZPET control tracking servo system for optical disk recording system does not include the low‐pass filter and its sampling time becomes faster. On the other hand, the sudden disturbance observer reduces the influence of nonperiodic disturbances. The experimental results point out that the proposed tracking servo system has a precise tracking response against both the periodic disturbances and the nonperiodic disturbances. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(4): 51–59, 2010; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20800     

Inertia moment identification in the average speed-type instantaneous speed observer

In recent servomotor control systems using highspeed microprocessors, it is difficult to obtain accurate speed information by using a low-resolution shaft encoder because encoder pulses are very sparse in the low-speed range. To overcome this problem, the instantaneous speed observer is proposed, system stability is improved, and strong disturbance rejection control is realized. However, when the inertia moment changes, the estimated instantaneous speed has error because the observer uses the nominal value of the inertia moment to calculate the instantaneous speed. For this reason, the identification method of the inertia moment for the “position input-type” speed observer is proposed but it operated at about 50 rpm speed command. This paper proposes some novel identification methods for the “average speed-input type” instantaneous speed observer and identifies the inertia moment in the very low speed range below 1 rpm.     

An observer‐based controller for a class of polynomial fuzzy systems with disturbance

In this paper, a new observer‐based controller for a class of polynomial fuzzy systems with disturbance is proposed. First, by some appropriate equivalence transformation of the polynomial fuzzy model, the first output‐sized states can be obtained directly from the output, which eventually enables us to obtain the feedback control gain and observer‐related parameters together without considering the so‐called separation principle. Second, with the disturbance in mind, a PI‐type observer is suggested. Finally, the sum of squares for the stability of the closed‐loop observer‐based control system is provided. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A disturbance‐decoupled adaptive observer and its application to faulty parameters estimation of a hydraulically driven elevator

In this paper, a disturbance‐decoupled adaptive observer is designed for the joint state‐parameter estimation of a system with unknown disturbance inputs. The proposed Robust Adaptive Observer (RAO) integrates an Unknown Input Observer (UIO) to the parameter estimation process, where the unknown parameters are estimated as extended states of the system. An auxiliary input is added to the UIO in coping with the estimation errors so that the exponential stability and convergence of the observer are guaranteed. The proposed observer is applied to a hydraulically driven elevator for the faulty parameter estimation. The simulation results show the accuracy of the observer and its robustness to both disturbances and measurement noises. Copyright © 2010 John Wiley & Sons, Ltd.     

A speed control method for a PM motor using a speed observer and a low‐resolution encoder

This paper proposes a new speed control method for a PM motor using a low‐resolution encoder and a speed observer. The servo system should be economical and simple. For this purpose, this paper realizes the high‐performance speed control system using a low‐resolution encoder, whose performance is nearly equal to the performance of speed servo system using a conventional optical encoder. The speed observer uses the information of motor current and motor voltage. The rotor position is calculated by the estimated value of speed observer. This observer has the influence of electrical parameter variation. This paper proposes the correction algorithm of both the voltage error of PWM inverter and the electrical parameter variation. The experimental results and numerical simulation results point out that the proposed speed control system has the desired speed response with respect to parameter variations and load torque perturbation. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(1): 66–75, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10121     

Fault‐tolerant saturated control for switching discrete‐time systems with delays

In this paper, fault‐tolerant control problem for discrete‐time switching systems with delay and saturated input is studied. Sufficient conditions of building an observer are obtained by using multiple Lyapunov function. These conditions are worked out using cone complementarity technique, to obtain LMIs with slack variables and multiple weighted residual matrices. The obtained results are applied on a numerical example showing fault detection, localization of fault, and reconfiguration of the control to maintain asymptotic stability even in the presence of a permanent sensor fault and saturation on the control. Copyright © 2014 John Wiley & Sons, Ltd.