Strong Disturbance Rejection Research Articles

IMPRESSION MANAGEMENT OF DEFICIENCIES AND DENIAL OF ILLNESS IN SCHIZOPHRENIA: RELUCTANCE TO EXPOSE MENTAL ILLNESS UNMODERATED BY ITS LEVEL OF ADVANTAGEOUSNESS

The control problem for a ship steering system with uncertain time delays is discussed in this paper. The system uncertainties, including parameters and delay variations as well as unmodeled dynamics, are taken as “internal disturbances”, while ocean movements are taken as “external disturbances”. The combination of the two is considered as the “total disturbances” of the system. With the aid of a modified Smith predictor, an extended state observer (ESO) is constructed to estimate the total disturbances. By compensating its effects in a closed loop, the system is reduced to a set of cascaded integrators, which can be easily handled. The advantages of the proposed approach lie in two aspects: (1) it does not need an accurate model of the system; (2) it is robust against delay variations. The simulation results validate the strong disturbance rejection capability of the proposed method.

Enhanced disturbance suppression in sampled-data systems and its application to high density data storage servos

Precise servo control systems require strong disturbance rejection capabilities for accurate positioning in the nanometer scale world today. In this paper, we propose an add-on DDO (disturbance decoupling observer) and DDOS (DO with extraneous sensor) for stronger disturbance suppression. Our proposed control methodology uses a nominal plant model and its inverse to reject input and output disturbances simultaneously in sampled-data systems. The plant inverse controller is approximated by tuning a single parameter ɛ. Experimental results on a PZT actuated servo system with air flow of mean speed of 50 m/s corresponding to 15,000 rpm in today’s high end hard disk drives show an improvement of 69.2% of 3σ PES (position error signal) during track-following.

Individual channel analysis of the turbogenerator with a power system stabilizer

A complete new insight into why excitation-governor control with power system stabilizers (PSSs) has been so successful for the control of turbogenerators connected to an infinite bus is provided by the small-signal multivariable analysis framework, individual channel analysis and design (ICAD). The multivariable analysis justifies treating the turbogenerator system as a pseudo-single-input single-output (SISO) system where the governor loop is first closed and the exciter loop is treated as a SISO system for the prime purpose of rejecting voltage disturbances. The function of the PSS is identified as that of overcoming an awkward switch-back frequency-domain characteristic of the excitation channel so as to - 1 permit high-performance excitation channel bandwidths up to 10 rad s that otherwise could not be obtained. Thus, in addition to the control requirements of set point regulation of the terminal voltage and shaft speed, the PSS provides for a second control requirement of strong voltage disturbance rejection over the - 1 important frequency range 0-10 rad s . The PSS control option is also assessed against other control options. Several other results concerning stability robustness to system uncertainties in different system configurations follow from the analysis in a transparent and immediate way.

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

AbstractIn 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.

Experimental evaluation of adaptive and robust schemes for robot manipulator control

In this paper, adaptive and robust control schemes are compared in the tracking control of robot manipulator. In adaptive control, the authors classify the adaptive control laws that have been proposed into three types. They show that the most important difference among them is that in their PD gains. They investigate their tracking performances by laboratory experiment and show that they can have similar performances by adjusting their equivalent PD gains almost equally. In robust control, two degree of freedom (TDOF) controller is examined. The authors demonstrate its strong disturbance rejection performance and robustness to parameter variation by experiment. They analyze the stability of TDOF controller against the payload change. Finally, through these experiments, they consider the advantages of adaptive and robust schemes for robot manipulator control.