Optimal Decoupled Disturbance Observers for Dual-Input Single-Output Systems

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Xu Chen ◽  
Masayoshi Tomizuka
Keyword(s):  
Disturbance Observer ◽  
Filter Design ◽  
Spectral Characteristics ◽  
Hard Disk Drives ◽  
Disk Drives ◽  
Single Input Single Output ◽  
Control Approach ◽  
Single Output ◽  
Dual Stage ◽  
Single Input

The disturbance observer (DOB) has been a popular robust control approach for servo enhancement in single-input single-output systems. This paper presents a new extension of the DOB idea to dual- and multi-input single-output systems, and discusses an optimal filter design technique for the related loop-shaping. The proposed decoupled disturbance observer (DDOB) provides the flexibility to use the most suitable actuators for compensating disturbances with different spectral characteristics. Such a generalization is helpful, e.g., for modern dual-stage hard disk drives, where enhanced servo design is becoming more and more essential in the presence of vibration disturbances.

Sequential vs. Parallel Synthesis for Dual-Stage Hard Disk Drives

2012 ◽  
Author(s):  
Craig E. Stensland ◽  
Mark Bedillion
Keyword(s):  
Controller Design ◽  
Hard Disk Drives ◽  
Voice Coil Motor ◽  
Hard Disk ◽  
Parallel Synthesis ◽  
Disk Drives ◽  
Parallel Design ◽  
High Bandwidth ◽  
Dual Stage ◽  
Single Input

Modern hard disk drives (HDDs) use single-input, dual-output (SIDO) controllers to control a dual-stage plant consisting of a large-stroke voice coil motor (VCM) and a short-stroke, high-bandwidth piezoelectric microactuator (PZT). Various methods have been proposed to perform the SIDO controller design; among the most commonly used approaches is μ-synthesis. While μ-synthesis generates stable controllers for the overall system, it does not guarantee stability of the VCM-only loop in the presence of microactuator saturation or failure. One approach to the DISO design that maintains VCM-only stability is the sequential design of VCM and PZT controllers. This paper presents a systematic study of sequential vs. parallel design. Designs are evaluated by comparing values of μ obtained for equivalent designs between the sequential and parallel approaches. The circle criterion is used to test stability of the system under saturation. Performance of sequential and parallel designs in shock events are tested in simulation.

Identification of Resonance Frequencies in Dual-Stage Hard Disk Drives: A Practical Strategy

2017 ◽  
Author(s):  
Minghui Zheng ◽  
Shiying Zhou ◽  
Masayoshi Tomizuka
Keyword(s):  
Hard Disk Drives ◽  
Control Process ◽  
Voice Coil Motor ◽  
Hard Disk ◽  
Disk Drives ◽  
Single Output ◽  
Main Challenge ◽  
Practical Strategy ◽  
Resonance Frequencies ◽  
Dual Stage

In hard disk drives (HDDs), there exist multiple mechanical resonances whose central frequencies may shift due to the change of environmental conditions such as the temperature. Such slowly varying resonance frequencies, if not handled properly, may degrade the positioning accuracy and even result in the instability of the closed-loop HDD system. Therefore, it is important to identify these resonance frequencies efficiently without interrupting the reading/writing process in HDDs. One main challenge of the frequency identification in a dual-stage HDD lies in the fact that it is a double-input-single-output (DISO) system. The outputs of the voice coil motor (VCM) and the piezoelectric microactuator (PZT) are coupled together. This paper proposes a practical strategy to identify the resonance frequencies in both the VCM and the PZT without disabling the PZT control process. Bandpass filters are utilized to separate the overall position error signal (PES) into several frequency segments based on priorly-known frequency range for each resonance. Two standard parameter adaptation algorithms are studied and discussed. Simulation results validate the effectiveness of proposed identification strategy.

scholarly journals Generalized Minimum Variance Control for MDOF Structures under Earthquake Excitation

2016 ◽  
Vol 2016 ◽  
pp. 1-11
Author(s):  
Lakhdar Guenfaf ◽  
Mohamed Azira
Keyword(s):  
Control Method ◽  
Minimum Variance ◽  
Soil Parameters ◽  
Seismic Excitations ◽  
Earthquake Excitation ◽  
Single Input Single Output ◽  
Control Approach ◽  
Single Output ◽  
Single Input ◽  
Siso Systems

Control of a multi-degree-of-freedom structural system under earthquake excitation is investigated in this paper. The control approach based on the Generalized Minimum Variance (GMV) algorithm is developed and presented. Our approach is a generalization to multivariable systems of the GMV strategy designed initially for single-input-single-output (SISO) systems. Kanai-Tajimi and Clough-Penzien models are used to generate the seismic excitations. Those models are calculated using the specific soil parameters. Simulation tests using a 3DOF structure are performed and show the effectiveness of the control method.

Robust Disturbance Rejection for a Class of Nonlinear Systems Using Disturbance Observers

2013 ◽  
Author(s):  
Ahmed H. El-Shaer ◽  
Abdulrahman H. Bajodah
Keyword(s):  
Nonlinear Systems ◽  
Disturbance Rejection ◽  
Disturbance Observer ◽  
Closed Loop ◽  
Inverted Pendulum ◽  
Single Input Single Output ◽  
Luenberger Observer ◽  
Single Output ◽  
Single Input ◽  
Bounded Disturbance

This paper is concerned with disturbance rejection performance in single-input single-output (SISO) nonlinear systems that are described by uncertain linear dynamics and bounded nonlinearities. First, the nonlinear terms are transformed into an equivalent bounded disturbance at the output of a linear system. Then, a disturbance observer (DOB) is added to the closed loop to achieve robust disturbance rejection. The DOB design is formulated as an extended Luenberger observer having internal dynamics with at least an eigenvalue at the origin. The synthesis of a (sub)optimal DOB is carried out by solving multi-objective H∞ sensitivity optimization. The design approach is applied to an inverted pendulum with actuator backlash. Closed loop response shows that tracking performance is indeed greatly enhanced with the DOB.

scholarly journals Multi-input multi-output fractional-order control of an underactuated continuum mechanism

2020 ◽  
Vol 17 (6) ◽  
pp. 172988142096957
Author(s):  
Bastian Deutschmann ◽  
Concepción A Monje ◽  
Christian Ott
Keyword(s):  
Rigid Body ◽  
Fractional Order ◽  
Nonlinear Feedback ◽  
Single Input Single Output ◽  
Control Approach ◽  
Fast Transient Response ◽  
Single Output ◽  
Single Input ◽  
Fractional Order Controller ◽  
The Continuum

This article treats the design and implementation of a multi-input multi-output fractional-order controller for a nonlinear system composed of a tendon-driven continuum mechanism. As the continuum can be deformed along all Cartesian directions, it is suitable for the application as a flexible neck of a humanoid robot. In this work, a model-based control approach is proposed to control the position of the head, that is, the rigid body attached to the top of the continuum mechanism. Herein, the system is modeled as a rigid body on top of a nonlinear Cartesian spring, with an experimentally obtained deflection characteristic which provides a simple and real-time capable model. By nonlinear feedback, the output dynamics are linearized and decoupled, which enables the design of single-input single-output fractional-order controllers for the regulation of each output independently. The design of a fractional-order [Formula: see text] controller is discussed to incorporate robustness and a fast transient response. The proposed control approach is tested in several experiments on the real system.

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