Disturbance-observer-based control (DOBC) and related methods have been researched and applied in various industrial sectors in the last four decades. This survey, at first time, gives a systematic and comprehensive tutorial and summary on the existing disturbance/uncertainty estimation and attenuation techniques, most notably, DOBC, active disturbance rejection control, disturbance accommodation control, and composite hierarchical antidisturbance control. In all of these methods, disturbance and uncertainty are, in general, lumped together, and an observation mechanism is employed to estimate the total disturbance. This paper first reviews a number of widely used linear and nonlinear disturbance/uncertainty estimation techniques and then discusses and compares various compensation techniques and the procedures of integrating disturbance/uncertainty compensation with a (predesigned) linear/nonlinear controller. It also provides concise tutorials of the main methods in this area with clear descriptions of their features. The application of this group of methods in various industrial sections is reviewed, with emphasis on the commercialization of some algorithms. The survey is ended with the discussion of future directions.

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Disturbance-Observer-Based Control and Related Methods—An Overview

Motion control is now recognized as a key technology in mechatronics. The robustness of motion control will be represented as a function of stiffness and a basis for practical realization. Target of motion is parameterized by control stiffness which could be variable according to the task reference. However, the system robustness of motion always requires very high stiffness in the controller. The paper shows that control of acceleration realizes specified motion simultaneously with keeping the robustness very high. The acceleration is a bridge to connect such robustness and variable stiffness. For practical applications, a technique to estimate disturbance is introduced to make motion controller to be an acceleration controller. Motion control of flexible structure and identification of mechanical parameters are also described.

Motion control for advanced mechatronics

Solid-state switch-mode rectification converters have reached a matured level for improving power quality in terms of power-factor correction (PFC), reduced total harmonic distortion at input AC mains and precisely regulated DC output in buck, boost, buck-boost and multilevel modes with unidirectional and bidirectional power flow. This paper deals with a comprehensive review of improved power quality converters (IPQCs) configurations, control approaches, design features, selection of components, other related considerations, and their suitability and selection for specific applications. It is targeted to provide a wide spectrum on the status of IPQC technology to researchers, designers and application engineers working on switched-mode AC-DC converters. A classified list of more than 450 research publications on the state of art of IPQC is also given for a quick reference.

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A review of single-phase improved power quality AC-DC converters

Tables of integrals

A new nonlinear disturbance observer (NDO) for robotic manipulators is derived in this paper. The global exponential stability of the proposed disturbance observer (DO) is guaranteed by selecting design parameters, which depend on the maximum velocity and physical parameters of robotic manipulators. This new observer overcomes the disadvantages of existing DOs, which are designed or analyzed by linear system techniques. It can be applied in robotic manipulators for various purposes such as friction compensation, independent joint control, sensorless torque control and fault diagnosis. The performance of the proposed observer is demonstrated by the friction estimation and compensation for a two-link robotic manipulator. Both simulation and experimental results show the NDO works well.

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A nonlinear disturbance observer for robotic manipulators

A torque sensorless control for a multi-degree-of-freedom manipulator is described. In the method, two disturbance observers are applied to each joint. One is used to realize a robust motion controller. The other is used to obtain a sensorless torque controller. A robust acceleration controller based on the disturbance observer is shown. To obtain the sensorless torque control, it is necessary to calculate the reaction torque when the mechanical system performs a force task. The calculation method for the reaction torque is explained. Then the method is expanded to workspace force control in the multi-degree-of-freedom manipulator. Several experimental results are shown to confirm the validity of the proposed sensorless force controller. >

Torque sensorless control in multidegree-of-freedom manipulator

The conventional proportional P controller has been often used as the position controller of the dc servo motor. When the unknown and inaccessible load torque, such as the coulomb friction, the gravity, and so on, is imposed on the dc servo motor, this control system has the steady-and/or transient-state error.

Microprocessor-Controlled DC Motor for Load-Insensitive Position Servo System

There are many works about bilateral teleoperation. However, good touch sense of remote object has not been realized in actual system yet. In this paper, the goals of bilateral teleoperation are considered as following two points. One is a reproduction of environmental impedance in master side. The other is a realization of small operational force. Operational force means the force the operator feels in addition to real environmental force. Corresponding to these goals, novel evaluation indices are defined which are named "reproducibility" and "operationality", respectively. Moreover, control stability must be satisfied. After all, bilateral teleoperation must satisfy three conditions such as reproducibility, operationality and stability. Using defined evaluation indices, bilateral controller is designed. Through analysis, it is confirmed that the three desired conditions in bilateral teleoperation are well satisfied with this controller. The effectiveness of this research is demonstrated by an experiment with bilateral forceps robot.

Reproducibility and operationality in bilateral teleoperation

The dynamics of the multi-degrees of freedom manipulator is highly nonlinear and the compensationagainst this nonlinearity should be indispensable. This paper proposes the decentralizedjoint control method based on the disturbance observer where the dynamical equation is not directly solved. By using the information of the acceleration, the nonlinear term in the dynamical equation is estimated without the mathematically complicated process, and as a result, the joints are able to be decoupled and controlled independently each other by using even 16 bit microprocessors. The simulated and experimented results are shown in the paper to confirm the industrial viability of this method.

Kouhei Ohnishi

Papers

Motion control for advanced mechatronics

Torque sensorless control in multidegree-of-freedom manipulator

Microprocessor-Controlled DC Motor for Load-Insensitive Position Servo System

Reproducibility and operationality in bilateral teleoperation

A Robust decentralized joint control based on interference estimation